For comparison, those 4-terabyte hard drives you can buy today are about 1
terabit per square inch. That's because, unlike this new system, they use
hundreds or thousands of atoms to store a single bit. "Every bit consists
of two positions on a surface of copper atoms, and one chlorine atom that we can
slide back and forth between these two positions," explained Sander Otte,
lead scientist at Delft University of Technology, in a news
release. Because chlorine on copper forms into a perfectly square grid, it's
easy (relatively, anyway) to position and read them. If the chlorine atom is up
top, that's a 1; if it's at the bottom, that's a 0. Put 8 chlorine atoms in a
row and they form a byte.

The data the researchers chose to demonstrate this was a fragment of a Feynman
lecture, "There's plenty of room at the bottom" (PDF) -- fittingly,
about storing data at extremely small scales. The chlorine-copper array is only
stable in a clean vacuum and at 77 kelvin -- about the temperature of liquid
nitrogen. Anything past that and heat will disrupt the organization of the
atoms. The research was published today in the journal Nature Nanotechnology.